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Is a unicode user agent legal inside an HTTP header?

Tags:

http

mysql

user-agent

An application I'm maintaining loads user agents extracted from web logs into a MySQL table column using the 'latin1' charset. Occasionally, it fails to load a user agent that looks like this:

Mozilla/5.0 (Iâ?; CPU iPhone OS 5_0_1 like Mac OS X) AppleWebKit/534.46 (KHTML^C like Gecko) Version

I suspect it's choking on Iâ?. I'm working to figure out if this should be supported, or if it's corruption introduced by the upstream logging system. Is this a legal user agent in a HTTP header?

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AndreiM Avatar asked Apr 30 '12 13:04

AndreiM

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2 Answers

RFC 2616 (HTTP 1.1) says that message header contents must be "consisting of either *TEXT or combinations of token, separators, and quoted-string". If you look at the definitions for TEXT etc you will find that legal characters are those with byte values not in the [0, 31] range and not equal to 127; therefore characters such as â are as far as I can tell legal as per the spec.

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Jon Avatar answered Oct 13 '22 08:10

Jon

Technically, octets > 127 are allowed in comments. RFC 2616 makes them default to ISO-8859-1, but HTTPbis (the upcoming revision of RFC 2616) has removed that rule so that sometimes in the distant future, we may be able to move to a sane encoding.

Recommendation: strip all octets > 127.

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Julian Reschke Avatar answered Oct 13 '22 09:10

Julian Reschke
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